JIT: Complete first-class callable lowering (#1230 follow-up) #1363

Summary

Finish JIT for strlen(...), Foo::bar(...), and object first-class callables where compile-time string is unknown.

Context

• Roadmap: #78, North Star 2 #1056
• Syntax matrix: docs/capabilities-syntax.md · Lint gaps: docs/unsupported-syntax.md

Acceptance criteria

• Parser + CFG lowering (php-cfg / Compiler)
• VM semantics + compliance or unit tests
• LLVM JIT lowering (or documented deferral in SelfHostBuiltinPolicy)
• AOT/self-host probe if on vm.php / compile.php path
• Row in docs/capabilities-syntax.md (regenerate via script/capability-syntax.php)

Related

See open language backlog #1238.